Noise reduction method and system

ABSTRACT

The present disclosure provides methods and systems for reducing noise induced in one or more components in a hearing aid. The present disclosure provides methods for reducing noise induced in telecoils.

FIELD

The present disclosure relates to hearing aids. More particularly, thedisclosure relates to methods for reducing noise in hearing aid. Evenmore particular the present disclosure relates to a method for reducingnoise in hearing aids where the noise is induced by an active componentin the hearing aid. Still further, the present disclosure relates tomethods for reducing noise in a telecoil, where the noise originatesfrom wireless communication.

BACKGROUND

Generally, hearing aids are susceptible to noise, and such noise canpropagate through the sound path and be delivered to the user, who mayperceive the noise as a nuisance or in worst case can hinder the hearingimpaired user in being helped to hear desired sounds.

In some instances audible noise may originate as electromagneticinterference induced in a component, such as a noise sensitivecomponent, in the hearing aid. This could e.g. be electromagneticsignals induced in a telecoil, or in any other susceptible coils-likestructure, or in other types of connection lines in the hearing aid,e.g. connection lines exposed to electromagnetic energy prior toanalogue-to-digital conversion, e.g. lines coming from a microphone.

In particular noise originating from wireless communication coming intoor going out from the hearing aid may be annoying to the user, thereforethere is a need to provide a solution that addresses at least some ofthe above-mentioned problems. Also, the present disclosure provides atleast an alternative to the prior art

SUMMARY

The method and device according to the present disclosure may be usedfor removing noise originating from advertising packages in Bluetooth,such as Bluetooth low energy, packages induced in the telecoil signal.However, other sources in the hearing instrument might as well inducingnoise into especially the telecoil and other components.

The methods described in the present disclosure may be advantageouslyapplied when the noise in the noise sensitive component is in theaudible-frequency range. This may for example occur in a hearing aidequipped with both a telecoil and a Bluetooth and/or Bluetooth LowEnergy system. It has been seen that especially advertising packages inBluetooth or Bluetooth Low Energy systems causes electromagnetic noiseto be induced in telecoil systems. Detecting and reducing this noise,which is audible for the user, enhances the user experience.

The present disclosure provides a signal processing method for reducingnoise induced in a component of a hearing aid. The hearing aid maycomprise a battery, an active component powered by the battery, a firstcomponent and a processor powered by the battery. The components poweredby the battery may be powered directly or via other components. Thefirst component may be a noise sensitive component. The processor may beconfigured to obtain a measure of power drain from the battery. Thepower drain may be based on current drain. The measure of power drainmay include monitoring or measuring current to/from an active component.The method may comprise a step of operating the component so as to causea power drain from the battery. The method may comprise a step of theprocessor monitoring a power usage of the battery. The method maycomprise a step of the processor determining, based on the current powerusage, if the component is in an active state or a non-active state. Themethod may include basing noise reduction on the current power usage, oran average power usage over a period of time. The noise reduction may bebased on both the current power usage and a signal from the firstcomponent. Further, provided the component is determined to be in anactive state, the processor may be configured to applying a noisereduction algorithm to reduce noise induced by the component into theaudio input signal to the processor.

This may be advantageous to be used in a system of a single hearing aidor in a binaural hearing aid system with two hearing aids.

The present disclosure also provides a method for reducing noise in acomponent of a hearing aid when the hearing aid is part of a binauralsystem of two hearing aids. The component may be configured to provide asignal. The component is susceptible to electromagnetic noise. The twohearing aids may be configured to communicate with each other, e.g.wirelessly or wired. The method may comprise exchanging informationderived from the component between the two hearing aids of the binauralhearing aid system. This allows each hearing aid to access informationregarding the signal from two separate components, and thereby select toprocess the signal with a lesser noise component. This may beadvantageous especially in systems where the noise is not present atprecisely the same points in time, or least where this situation is lesslikely to occur. Additionally further noise reduction schemes may beemployed.

The present disclosure also provides a method for reducing noise in acomponent of a hearing aid where a processor of the hearing aid, or aprocessor connected thereto, is adapted or configured to analyze thesignal to detect onset of a noise causing event. This noise causingevent could be the transmission of a package in a radio frequency systemwhich causes noise to be induced in a coil or other susceptiblecomponent or lead in the hearing aid. The onset may be detected based ona comparison of a signal from the component, such as a telecoil, and anaudio signal from an input transducer of the hearing aid, such as amicrophone or microphone system. Alternatively, the onset may bedetected based on a comparison of a signal from the component, such as atelecoil, and a similar signal from another hearing aid in the vicinityof the hearing aid, e.g. a second hearing aid in a binaural hearing aidsystem. Exchanging such signals between two hearing aids would alloweach hearing aid to base an onset detection from the local componentsignal, e.g. the local telecoil signal.

The component may e.g. be a telecoil, a receiver or a microphone. Thesecomponents may be especially sensitive to electromagnetic noise, and maybe hard to shield physically from the electromagnetic induced noise.

An estimate of the induced noise may be predetermined and stored beforebeing used for reducing or removing the induced noise.

The noise contribution from the supply current may be estimated byaveraging over different instances of the noise

An average waveform may be trained in advance or during startup of thehearing instrument, or while the hearing instrument is in a program,where the component is not used.

The method may further comprise measuring the supply current and mayalso include establishing an estimate of the current influencing themagnetic field in the telecoil.

The supply current or changes in the supply current may be estimatedbased on a measurement of a resistor or transformer or by any othercurrent measurement techniques, such as by use of a Hall sensor

Further, the present disclosure provides a hearing aid comprising abattery, an active component powered by the battery, a first componentand a processor powered by the battery, the processor configured toobtain a measure of power drain from the battery, wherein the activecomponent is configured to be operated so as to cause a power drain fromthe battery. The power drain may be based on current drain. The measureof power drain may include monitoring or measuring current to/from anactive component. The hearing aid may be configured so that theprocessor is configured for monitoring a power usage of the battery, andthe processor configured to determining, based on the current powerusage, if the component is in an active state or a non-active state, andprovided the component is determined to be in an active state, theprocessor is configured to applying a noise reduction algorithm toreduce noise induced by the active component into an audio input signalprovided from the first component to the processor. Such a hearing aidmay provide an improved noise reduction and/or noise immunity when theuser is listening to a signal originating from the first component.

The active component may include a radio frequency transceiver. This maye.g. be a Bluetooth and/or a Bluetooth Low Energy based system, or evena proprietary based system. Further, the hearing aid may include severalactive components, such as multiple radio frequency transceivers and/orreception devices and/or other active components such as a soundprocessor and/or sound amplifier.

Active Component May be a Speaker in the Hearing Aid

The first component may be at least one of a coil, a telecoil, or amicrophone. Inducing electromagnetic noise in one or more of thesecomponents may cause the noise to be audible to the user, as thesecomponents usually in some way provide an input signal representing asound that the user is to be presented with.

The features and steps described herein may be combined as appropriate.

BRIEF DESCRIPTION OF DRAWINGS

The aspects of the disclosure may be best understood from the followingdetailed description taken in conjunction with the accompanying figures.The figures are schematic and simplified for clarity, and they just showdetails to improve the understanding of the claims, while other detailsare left out. Throughout, the same reference numerals are used foridentical or corresponding parts. The individual features of each aspectmay each be combined with any or all features of the other aspects.These and other aspects, features and/or technical effect will beapparent from and elucidated with reference to the illustrationsdescribed hereinafter in which:

FIGS. 1 to 24 disclose various method steps and signals at differentinstances in time and systems.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations. Thedetailed description includes specific details for the purpose ofproviding a thorough understanding of various concepts. However, it willbe apparent to those skilled in the art that these concepts may bepractised without these specific details. Several aspects of theapparatus and methods are described by various blocks, functional units,modules, components, circuits, steps, processes, algorithms, etc.(collectively referred to as “elements”). Depending upon particularapplication, design constraints or other reasons, these elements may beimplemented using electronic hardware, computer program, or anycombination thereof.

The electronic hardware may include microprocessors, microcontrollers,digital signal processors (DSPs), field programmable gate arrays(FPGAs), programmable logic devices (PLDs), gated logic, discretehardware circuits, and other suitable hardware configured to perform thevarious functionality described throughout this disclosure. Computerprogram shall be construed broadly to mean instructions, instructionsets, code, code segments, program code, programs, subprograms, softwaremodules, applications, software applications, software packages,routines, subroutines, objects, executables, threads of execution,procedures, functions, etc., whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.

A hearing aid may be adapted to improve or augment the hearingcapability of a user by receiving an acoustic signal from a user'ssurroundings, generating a corresponding audio signal, possiblymodifying the audio signal and providing the possibly modified audiosignal as an audible signal to at least one of the user's ears. The“hearing aid” may further refer to a device such as an earphone or aheadset adapted to receive an audio signal electronically, possiblymodifying the audio signal and providing the possibly modified audiosignals as an audible signal to at least one of the user's ears. Suchaudible signals may be provided in the form of an acoustic signalradiated into the user's outer ear, or an acoustic signal transferred asmechanical vibrations to the user's inner ears through bone structure ofthe user's head and/or through parts of middle ear of the user orelectric signals transferred directly or indirectly to cochlear nerveand/or to auditory cortex of the user.

The hearing aid is adapted to be worn in any known way. This may includei) arranging a unit of the hearing aid behind the ear with a tubeleading air-borne acoustic signals into the ear canal or with areceiver/loudspeaker arranged close to or in the ear canal such as in aBehind-the-Ear type hearing aid, and/or ii) arranging the hearing aidentirely or partly in the pinna and/or in the ear canal of the user suchas in a In-the-Ear type hearing aid or In-the-Canal/Completely-in-Canaltype hearing aid, or iii) arranging a unit of the hearing aid attachedto a fixture implanted into the skull bone such as in Bone AnchoredHearing Aid or Cochlear Implant, or iv) arranging a unit of the hearingaid as an entirely or partly implanted unit such as in Bone AnchoredHearing Aid or Cochlear Implant.

A “hearing system” refers to a system comprising one or two hearingaids, and a “binaural hearing system” refers to a system comprising twohearing aids where the devices are adapted to cooperatively provideaudible signals to both of the user's ears. The hearing system orbinaural hearing system may further include auxiliary device(s) thatcommunicates with at least one hearing aid, the auxiliary deviceaffecting the operation of the hearing aids and/or benefitting from thefunctioning of the hearing aids. A wired or wireless communication linkbetween the at least one hearing aid and the auxiliary device isestablished that allows for exchanging information (e.g. control andstatus signals, possibly audio signals) between the at least one hearingaid and the auxiliary device. Such auxiliary devices may include atleast one of remote controls, remote microphones, audio gateway devices,mobile phones, public-address systems, car audio systems or musicplayers or a combination thereof. The audio gateway is adapted toreceive a multitude of audio signals such as from an entertainmentdevice like a TV or a music player, a telephone apparatus like a mobiletelephone or a computer, a PC. The audio gateway is further adapted toselect and/or combine an appropriate one of the received audio signals(or combination of signals) for transmission to the at least one hearingaid. The remote control is adapted to control functionality andoperation of the at least one hearing aids. The function of the remotecontrol may be implemented in a SmartPhone or other electronic device,the SmartPhone/electronic device possibly running an application thatcontrols functionality of the at least one hearing aid.

In general, a hearing aid includes i) an input unit such as a microphonefor receiving an acoustic signal from a user's surroundings andproviding a corresponding input audio signal, and/or ii) a receivingunit for electronically receiving an input audio signal. The hearing aidfurther includes a signal processing unit for processing the input audiosignal and an output unit for providing an audible signal to the user independence on the processed audio signal.

The input unit may include multiple input microphones, e.g. forproviding direction-dependent audio signal processing. Such directionalmicrophone system is adapted to enhance a target acoustic source among amultitude of acoustic sources in the user's environment. In one aspect,the directional system is adapted to detect (such as adaptively detect)from which direction a particular part of the microphone signaloriginates. This may be achieved by using conventionally known methods.The signal processing unit may include amplifier that is adapted toapply a frequency dependent gain to the input audio signal. The signalprocessing unit may further be adapted to provide other relevantfunctionality such as compression, noise reduction, etc. The output unitmay include an output transducer such as a loudspeaker/receiver forproviding an air-borne acoustic signal transcutaneously orpercutaneously to the skull bone or a vibrator for providing astructure-borne or liquid-borne acoustic signal. In some hearing aids,the output unit may include one or more output electrodes for providingthe electric signals such as in a Cochlear Implant.

FIG. 1 shows a hearing aid system comprising different communicationsystems. The hearing aid system includes of two hearing instruments as abinaural hearing aid system.

Each instrument have at least three different communication systems: Amagnetic inductive link for communication over short distances (such asbinaural communication), an Radio Frequency (RF) system (Bluetooth LowEnergy (BLE)) link for communication with other devices (such as amobile phone), and a telecoil for picking up an electromagnetic fieldfrom a loop system.

The electromagnetic field picked up by the telecoil is then convertedinto a sound which is presented to the listener. One problem with theseclosely spaced communication systems is that they may interfere withother. In particular, the signal received by the telecoil may bepolluted by noise from the RF system, e.g. while the RF system istransmitting advertising packages or the like. Such an interfering noisesignal is shown in FIG. 2. The advertising noise is periodic, but withsome random jittering.

In addition to the above shown communication systems, the hearing aidsystem may as well include an FM receiver, or be connected to one via anadaptor.

FIG. 2 illustrates an example of a received telecoil signal polluted byinterfering noise from Bluetooth low energy advertising. The advertisingnoise in Bluetooth Low Energy is generally periodic with some jitter.

It may be possible to take advantage of the fact that a binaural systemwith two hearing aid provides two telecoil signals in the case whereboth hearing instruments are equipped with a telecoil. The hearinginstruments are furthermore equipped with a system for transmitting andreceiving audio signals between the hearing instruments.

The advertising noise is not likely to occur at the same time at bothhearing instruments. As both hearing instruments receives the telecoilsignal, it is likely that one of the received telecoil signals are notcontaminated by the advertising noise. By exchanging the two obtainedtelecoil signals, each hearing instrument has access to two instances ofthe telecoil signal.

Hereby, it is less likely that both instances of the telecoil signal iscontaminated by the advertising noise during the same time frame. Thisis illustrated in FIG. 3. FIGS. 3 to 7 illustrates how a possible systemfor telecoil noise enhancement may look like.

A general solution could be an adaptive weighted sum between the twotelecoil signals. The weighted sum can be implemented in the time domainor in the frequency domain. The weighted sum may be implemented as anMVDR beamformer such as a generalized sidelobe canceler given byY_(TC)=C₁−βC₂, where C₁ is given by the sum of the two telecoil signals,and C₂ is given by the difference between the two microphone signals,and

${\beta = \frac{\left\langle {C_{1}C_{2}^{*}} \right\rangle}{\left\langle {C_{2}}^{2} \right\rangle}},$where

denotes a time average and * denotes a complex conjugation. The estimateof beta may be overruled by, or dependent on, a control signal whichprovides information on when the telecoil system may be contaminated bynoise from the Bluetooth system. Alternatively, the averaging timeconstant may depend on the control signal. Hereby not only the BLEintroduced noise may be attenuated but also other contributions totelecoil noise.

The Bluetooth advertising noise may be active at different times in thetwo hearing instruments. It is an advantage to have non-overlappingadvertising noise between the two hearing instruments as it hereby maybe possible to provide that at least one of the received telecoilsignals at a given time frame is not contaminated by noise introduced bythe Bluetooth system.

In FIG. 3, the bars illustrate the occurrence of advertising noise in atelecoil signal obtained at a left and right hearing instrument. Eachoccurrence is periodic with random jittering, within the time indicatedby the arrows. As illustrated the occurrence of advertising noise isdifferent at the two hearing instruments.

FIG. 4 illustrates an example showing how noise-induced time frames ofthe telecoil signal are substituted by ‘clean’ time frames obtained atthe opposite instrument.

FIG. 5 illustrates an alternative to simply substituting the telecoilsignal from the opposite instrument, the Figure present a combination ofthe left and the right telecoil signals. E.g. by a weighted sum of thetwo obtained signals.

FIG. 6 is a schematic illustration of an implementation of the systemshown in FIG. 4. The telecoil signals are exchanged between the twohearing instruments, and based on a control signal (ctrl) on when noisefrom the Bluetooth system is expected to contaminate the telecoil signalwith noise, the instance of the telecoil signal without noise can beselected and presented to the listener. Preferably, the same telecoilsignal is presented to both hearing instruments, more or lesssimultaneously. Hereby, the remaining background noise within thetelecoil signal (not originating from the Bluetooth system) will notswitch between being similar and different. Hereby the introduction ofspatial artifacts is avoided.

FIG. 7 illustrates a schematic implementation of the system illustratedin FIG. 5, i.e. a generalization of the proposed system shown in FIG. 6.The two telecoil signals are combined by a weighted sum. The weights maybe real scalar values, the weights may be real-valued filtercoefficients in the time domain or complex-valued filter coefficients inthe frequency domain. The weights may be adaptive, e.g. estimated as anMVDR beamformer, The MVDR beamformer may be e.g. be implemented as ageneralized sidelobe canceller.

Further, in an alternative, or combination with other methods describedherein, a method may use information other than when the radio isactive. Instead, the onsets of the noise may be estimated. Preferably,only onsets present in the telecoil signal, but absent in the audiosignal should be estimated. This is illustrated in FIG. 8.

FIG. 8 schematically illustrates noisy spikes in the telecoil signalwhich may be detected by an onset detector. Preferably, the onsetdetector has access to both audio and telecoil input. The objective ofthe onset detector is to detect onsets present in the telecoil signal,but absent in the audio signal. Hereby, noise onsets from the Bluetoothsystem can be distinguished from onsets present in the audio. Theresulting onset flag (or probability of onset) is used to control thefading between the telecoil signal and the audio signal).

As an alternative to the local onset detection, an onset may beestimated based on both the local telecoil signal T and the telecoilsignal T′ obtained at the hearing instrument at the opposite ear inbinaural system, however, the method may be used in a signal hearing aidwithout the need of a second hearing aid. As the noise induced onsetsare unlikely to coincide at two hearing aids, it is possible detect, orat least estimate, the onset in both telecoil signals and fade to thetelecoil signal where the onset is not present. This is illustrated inFIG. 9. The audio signal may as well be used as input to the onsetdetector. The detector may be implemented in the time domain or indifferent frequency channels.

FIG. 9 illustrates an onset which may be detected from both a locallyreceived telecoil signal and the telecoil signal received at theopposite ear, and retransmitted to the local ear via anothercommunication channel. The onset detector detects onsets in the telecoilsignals and fade to the signal with no onset. The audio input may beused in addition to the telecoil signals to detect if the onset ispresent in the microphone signal as well.

A further alternative or addition provides a method using the receivedtelecoil signal solely as a control signal. As the telecoil signal isassumed to have a higher SNR compared to the audio signal, it can beused to derive a fast-varying gain in the time-frequency domain, whichcan be applied to the audio signal in order to enhance the audio signal.In this way, the telecoil-signal-derived-gain becomes a vocoder (themethod may work less optimal for music picked up by the telecoil). Inthis case, the control flag form the Bluetooth system may be used to“clean” the telecoil signal before the vocoder gain is estimated. Anexample drawing of this system is shown in FIG. 10.

FIG. 10 illustrates a system where the telecoil signal is assumed tohave a high, positive SNR, the signal can be used to enhance themicrophone signal contrary to listening to the telecoil signal itself.First the noise originating from the RF system is removed using accessto when the RF signal is transmitting or receiving. This can be appliedin the time domain (as shown) or in the frequency domain. In thetime-frequency domain (after the analysis filterbank), energetic areasof the telecoil signal can be estimated and the energetic areas can beconverted into a gain applied to the microphone signal, wherein the gainpreserves the energetic areas of the telecoil signal.

In a still further method, as either an alternative or addition theother methods disclosed herein, the method may avoid applying theinformation directly from the BLE system, but apply another signal foractivation of telecoil noise removal. The root cause of the telecoilnoise may, as outlined herein, be magnetic field due to the changes inthe supply current. This is illustrated in FIG. 11. Especially when theRF system is active, the supply current will change. The advantage ofmeasuring the supply current changes over using information on when theRF system is active is that other sources of current induced telecoilnoise besides the RF system is detected as well. Furthermore, the supplycurrent changes may have a more accurate time alignment with thetelecoil artifacts than the provided

FIG. 11 illustrates changes in the supply current causing telecoil noisedue to the magnetic field induced in the telecoil.

By measuring the supply current, it is possible to estimate the currentinfluencing the magnetic field in the telecoil. The supply current orthe changes in the supply current can be estimated in various ways, e.g.resistor or transformer based as illustrated in FIG. 12, or by any othercurrent measurement techniques, e.g. by use of a Hall sensor.

FIG. 12 illustrates current (or time-varying changes in current) in thesupply wire which may be measured by a resistor or a transformer-basedmethod or other methods. In addition to the shown methods, the currentmay be measured by a Hall sensor or any other current measurementtechnique. The DSP is used to sample the supply current and to predictthe telecoil artifacts.

FIG. 13 illustrates a frequency domain implementation of the proposedtelecoil noise removal algorithm. Assuming a linear relationship betweenthe changes in the supply current and the magnetically induced telecoilnoise, it may be possible to implement the noise removal algorithm as anMVDR beamformer using a generalized sidelobe cancelling structure. Thesupply current (difference), X_(SC)(k) is actually a telecoil noiseestimate, assumed not to include any target signal, whereas the telecoilsignal X_(TC)(k) includes the target signal and the magnetically inducednoise. Preferably, the DC component has been removed from the supplycurrent. The aim is to subtract a scaled and phase-aligned estimate ofthe noise, i.e.Y(k)=X _(TC)(k)−β(k)X _(SC)(k)

This thus scale the noise estimate (i.e. the supply current) by acomplex-valued factor β. It is possible to estimate beta (omitting thefrequency index k) as

${\beta = \frac{\left\langle {X_{TC}X_{SC}^{*}} \right\rangle}{\left\langle {X_{SC}}^{2} \right\rangle + c}},$where * denotes the complex conjugation and

denotes the statistical expectation operator, and c is a constant. Wemay e.g. implement the expectation in terms of a first order IIR filter,i.e. the expectation for |X_(SC)(m)|² may be implemented as

|X _(SC)(m)|²

=λ|X _(SC)(m)|²+(1−λ)

|X _(SC)(m−1)|²

where m is the frame index λ is a coefficient given byλ=1−e ^(−1/(f) ^(s) ^(τ)),in which f_(s) is the frame rate and τ is the time constant. Preferablythe time constant τ is greater than 10 milliseconds, such as greaterthan 100 milliseconds, such as greater than 1 second or 5 seconds. TheIIR filters is preferably only updated, while the noise is present, ortarget is absent, i.e.

$\left\langle {{X_{SC}(m)}}^{2} \right\rangle = \left\{ \begin{matrix}{{{\lambda{{X_{SC}(m)}}^{2}} + {\left( {1 - \lambda} \right)\left\langle {{X_{SC}\left( {m - 1} \right)}}^{2} \right\rangle}},} & {{noise}\mspace{14mu}{present}} \\{\left\langle {{X_{SC}\left( {m - 1} \right)}}^{2} \right\rangle,} & {otherwise}\end{matrix} \right.$

The IIR filters are advantageously updated in the periods with presenceof noise peaks. The IIR filters may be updated based on when the RFsystem is communicating. The periods where the RF system iscommunicating may be detected or determined based on monitoring thepower drain and/or current drain. This could for instance be achieved bymonitoring power consumption of one or more components in the hearinginstrument. The current or power draw could be measured and/or monitoreddirectly at the battery. The current or power draw could be measuredand/or monitored directly at the active component or at componentsconnected thereto.

Alternatively, the noise may be detected directly from the supplycurrent signal, e.g. while the supply current is above a certainthreshold. Alternatively the time constant τ or the coefficient λ may bea direct function of the supply current, e.g. as illustrated in FIG. 14.

Further alternatively, or additionally, the noise estimate may beupdated based on information from the RF system, i.e. the wirelessinterface, either directly or via a secondary source, so that the noisereduction may be targeted and/or changed and/or enhanced and/orinitiated in or around periods of time where the wireless interface isknown to be active, or at least when the RF system is in advertisingmode. This information, i.e. the information that the radio is intendedto be active, could be used to trigger the here-in mentioned noisereduction method.

Even further, the update of the noise estimate may be based on thedetector looking for clicking sounds, such as illustrated in FIG. 13.

FIG. 14 illustrates the IIR filter coefficient may λ depend on the levelof the supply current (with its DC component removed). At low levels, nonoise is present, hence no current influences the telecoil, and thepower estimate (and hereby β) is not updated as the coefficient λ iszero. At higher levels, the telecoil is influenced by the supplycurrent, and the IIR filter is updated with the coefficient limited atthe value λ_max.

As the influence of the telecoil from the supply current is differentfrom instrument to instrument, and depend on many factors, it may benecessary to calibrate e.g. the threshold. The threshold may beestimated in controlled situations. The current may e.g. be measured intime frames, where the RF system is active. Hereby the threshold may beadjusted according to the maximum amount of variation in the measuredsupply current. The threshold may be depending on the type of RF signal(e.g. different TX/RX modes such as advertising signals, control signalsor data exchange signals).

The proposed method may as well be implemented in the time domain asillustrated in FIG. 15

As another alternative to the above, it could be possible to subtract afixed waveform, which has been estimated in advance. Subtracting a fixedwaveform may be advantageous, if the relationship between the supplycurrent and the magnetically induced telecoil is non-linear. Based onthe detection of the supply current a scaled and time-aligned estimateof the supply current induced waveform received by the telecoil may besubtracted from the noisy signal. This is illustrated in FIG. 17. Thenoisy waveform is identified from the supply current, and for eachinstance of the noisy waveform, the (possibly scaled) average waveformmay then be subtracted. Depending on the transceiving mode, differentwaveforms may be subtracted.

The average waveform may be trained in advance or during the startup ofthe hearing instrument, or while the hearing instrument is in a programwhere the telecoil is not used. The training may e.g. be based on aspecial RF tranceiving sequence, where the telecoil signal is exposed toall types of RF-induced noise. The trained waveforms may e.g. be storedin in the instrument or in an external device. The waveforms may bestored in advance, and only the variance of the noisy signal is trained.The estimation of an average waveform is illustrated in FIG. 18. Theestimation is here based on averaging (e.g. by use of a first order IIRfilter) of the (time-aligned) telecoil signal frames, where the noise isidentified to be active. The identification may be based on detection ofthe signal in the supply current or it can be based on when the RFsystem is active. Depending on the RF transceiving mode, differentwaveforms may be trained.

FIG. 16 is a general illustration of noise removal based on the supplycurrent estimate. Noise removal may be applied by a gain reduction, orsubtraction an estimate of the noise, e.g. obtained by a linearfiltering of the supply current or obtained by subtraction of apre-trained waveform of the estimated noise obtained by the telecoil.

FIG. 17 illustrates a situation where, from the supply current estimate,the noisy parts of the telecoil signal are identified. At each instanceof identified noise, the waveform generated by the noise is subtractedfrom the noisy telecoil signal. Assuming the noise is caused by the RFsystem, different noisy waveforms can be subtracted, depending on the RFtranceiving mode.

FIG. 18 illustrates the waveform of the noise contribution from thesupply current that may be estimated by averaging over differentinstances of the noise. The instances may either be detected from themeasured supply current. Alternatively, the instances may be identifiedby information on whether RF is active. Different waveforms may betrained based on the RF transceiving mode (e.g. advertising, datatransmission, communication of control signals)

FIG. 19 illustrates an RF system positioned in the vicinity of a coil.The arrows from the RF transmitter on the left hand represent atransmitted signal, which causes a current to be induced in the coil,here a telecoil. Various mechanical arrangements may be provided toreduce the current induced in the telecoil. Such arrangements mayinclude a screen e.g. provided at an end of the telecoil so as to reducethe flow of energy originating in connection with the RF system into thetelecoil. Also, some parts of the electrical leads in the hearing aidmay be arranged so as to induce a magnetic field that is orientatedopposite of the electromagnetic noise originating from the RF system.This could be in the form of loops, either full loops or part of loops,or the like formed by the leads in e.g. a printed circuit board.

FIG. 20 is similar to FIG. 19, with the addition of a componentarranged, or configured, to estimate when current is induced. Asdescribed above, this could be an arrangement where a current in aresistor or capacitor is monitored or measured, or use of another typeof probe, such as a Hall probe or the like.

As the hearing aid is operated in a way that causes a power drain asexplained herein, the output signal provided to the user, either as anacoustical signal from a speaker unit, as an inductive signal to animplanted part, a signal to drive a bone anchored output transducer, maybe subject to noise caused by this power drain. The power drain inducednoise may exhibit a pulsating pattern, which may be alleviated by themethod as described in the present description. Thus, monitoring thesignal driving the output transducer may trigger an update of the noiseestimate. The monitoring may e.g. be performed in the sound processor ora device connected thereto.

FIG. 21 illustrates the situation where the telecoil signal is onlyreceived by one hearing instrument, in which the communication unitcausing noise has been disabled. The received telecoil signal isre-transmitted to the opposite (contralateral) hearing instrument via acommunication link which do not cause noise in the telecoil signal, e.g.transmitted at a different frequency and/or different type oftransmitter/receiver unit. In the other (the contra lateral) instrument,the communication unit causing noise in the telecoil is enabled, but thetelecoil is either absent or disabled or simply ignored in theprocessing. Hereby a binaural hearing system comprising two hearinginstruments is established where one instrument is used for receivingtelecoil signals, and the other instrument may be used to receivesignals from other external devices. The signals are afterwardsexchanged between the instruments. Preferably using a communicationchannel that do not introduce (substantial) noise in the telecoilsignal, such as a magnetic induction system.

In general, a communication channel used in parallel to the telecoilsignal could exhibit low or no introduction of noise in the telecoilsignal if it does not produce current peaks in the same manner as aBluetooth-based system, such as a Bluetooth Low Energy based system.

FIG. 22 illustrates a system where in one device an RF system is disableand a telecoil signal is enabled where in the other, contralateralhearing aid, an RF signal is enabled and a telecoil signal is disabled.It could be envisioned to use e.g. an inductive communication system forcommunicating between the two hearing aids.

Yet another option is to place the telecoil receiver in an externaldevice, such as illustrated in FIGS. 23 and 24, which external device isthen configured to re-transmit the telecoil signal to the one or morehearing instruments. This could be done either by an RF communicationmethod, which potentially causes noise in the telecoil in the externaldevice, however, it is easier to place a telecoil in an external deviceso that it is not polluted by noise as external devices usually are muchlarger than hearing aid, or to transmit the signal by e.g. a magneticlink, which have been shown to exhibit lower interference to thetelecoil signal.

As the hearing instrument is to be used in any environment, the hearingaid may be subject to external noise, that is, noise impinging on thedevice, in this context, impinging electromagnetic noise. Suchexternally radiated noise may be dealt with as it may corrupt or degradethe telecoil signal.

In an area with multiple persons, e.g. two or more persons, each wearingat least one hearing aid, e.g. two persons in the same room, such as aclassroom, church or cinema or the like, each having at least onehearing aid, such at least two hearing aid could be configured tocooperate so that one hearing aid is configured to transmit the telecoilsignal to the other hearing aid worn at the other person.

This could create a mesh-network of multiple hearing aids or external(auxiliary) devices, where the signal presented to the wearer is acombination of telecoil signals from all/both of the devices. Themesh-network could also be termed an ad-hoc network. Advantageously, thenetwork could be created using a communication channel that did notcause noise, or at least had limited impact, in the telecoil signal.

Such a system could be contemplated to have lower transmission loss whentransmitting to a neighboring hearing aid at another person compared totransmission to a contralateral hearing instrument.

One possible way of treating the telecoil signal could include replacingthe signal with a random signal upon detecting a transmission even asdescribed herein. The detection of the event by examining e.g. the powerdraw from the active component could prompt a processor receiving thesignal from the telecoil with a replacement signal, e.g. for theduration of the event or at least for a part of the event. Thisreplacement signal could be at a random level, or could be selectedbased on the level of the signal in a period prior to the event, such aswithin a few milliseconds or the like. The frequency content of thesignal could also be at least partially random and/or selected based ontelecoil signals received in a period prior to the event. The signal maybe replaced by a signal having a predefined (fixed) level, or a levelwithin a fixed interval, i.e. within a given range from a predefinedcenter level.

When two hearing instruments, i.e. a binaural hearing system, where eachhearing instrument has an active component being a radio, the two radiosof the binaural hearing system may be configured so that an offset intime is established between an advertising event in the respectivehearing instrument. This means that the two hearing instrumentscoordinate when each of them are allowed to transmit an advertisingevent. By timing the advertising even so that the event in the twohearing instruments do not overlap in time, at least one of the hearinginstruments is able to pick up a telecoil signal not being polluted bynoise from this particular event. This could also be applied to otherevents that occur in both hearing instruments. The offset could bedefined as a fraction of the (expected) time between events. If bothhearing instrument radios transmit an advertising event with a fixedtime interval, and the time interval is the same for the two radios, theoffset in one device relative to the other could be in the range of 1 to90% of the time between events, such as 10 to 80%, such as 25 to 50% orother suitable interval. This is also illustrated in connection to FIG.3.

Advantageously, one of the hearing instruments may be configured to NOTadvertise, or alternate advertising, via a different communicationchannel, e.g. with the other device acting as a proxy for thatinstrument. This could eliminate the advertising noise in one hearinginstrument, and this hearing instrument could then be selected as theinstrument dedicated to receive telecoil signals, which are then sharedwith the other hearing instrument via a different communication channel.

The transmission between two hearing instruments located at respectiveopposite sides of the head of the user may be performed via a third,external, device, such as illustrated in FIGS. 23 and 24. In such asetup, the telecoil signal is picked up by one hearing instrument andforwarded to an external device, which then transmits the signal to theother hearing instrument. The external device may act as a replystation, simply relaying the received signal, or it may process thesignal, e.g. reduce noise or process the signal in other ways, e.g.enhance intelligibility. The transmission of the telecoil signal fromthe hearing instrument picking up the signal may be performed via acommunication channel that does not add any substantial noise to thetelecoil signal, at least during the transmission of the signal from thehearing instrument to the external device. The communication channel, ormedium, between the hearing instrument and the external device may bethe same for the two hearing instruments, or alternatively, be twodifferent channels or mediums.

An external device as described above may include a Bluetooth Low Energyprotocol, BLE, and may include a telecoil. In such an external device, atransmission/reception flag may be raised by a wireless interface, suchas flags from the BLE radio, may be used to trigger noise reductionalgorithm for the telecoil signal. This could be advantageous when theexternal device is at least one of the elements receiving telecoilsignal.

In a binaural system with an additional, auxiliary, external device, (atleast) three elements in the system may include a telecoil for pickingup a telecoil signal. A cleaned signal may be established from suchthree telecoils, possibly based on just two of the received telecoilsignals. The decision on which of the signal to base an output signal,may include examining each signal for noise, such as noise from anadjacent, such as internal, radio and/or noise in the telecoil signalfrom other sources, such as external sources. The external noise sourcescould include electromagnetic noise sources.

As the noise reduction described in present disclosure is adaptive, ithas the further advantage that even though the battery may appear to besymmetrical, as most batteries used in hearing aids are basicallycylindrical, the current drawn from the battery may not be constant,partly due to the internal structure of the battery causing a differentmagnetic field to be generated, or that the current drawn from thebattery may change as a function of the state of the battery, such ascharge state or age or other factors, the adaptiveness of the algorithmallow for constant noise cancellation or at least noise reduction is allor most situations.

The methods described herein may be applied to hearing aids withdifferent kinds of output transducers. The methods described herein maythus be applied to hearing aids with airborne acoustic output as well ascochlear output transducer and bone anchored hearing aids alike.

A Cochlear Implant typically includes i) an external part for picking upand processing sound from the environment, and for determining sequencesof pulses for stimulation of the electrodes in dependence on the currentinput sound, ii) a (typically wireless, e.g. inductive) communicationlink for simultaneously transmitting information about the stimulationsequences and for transferring energy to iii) an implanted part allowingthe stimulation to be generated and applied to a number of electrodes,which are implantable in different locations of the cochlea allowing astimulation of different frequencies of the audible range. Such systemsare e.g. described in U.S. Pat. No. 4,207,441 and in U.S. Pat. No.4,532,930.

In an aspect, the hearing aid comprises multi-electrode array e.g. inthe form of a carrier comprising a multitude of electrodes adapted forbeing located in the cochlea in proximity of an auditory nerve of theuser. The carrier is preferably made of a flexible material to allowproper positioning of the electrodes in the cochlea such that theelectrodes may be inserted in cochlea of a recipient. Preferably, theindividual electrodes are spatially distributed along the length of thecarrier to provide a corresponding spatial distribution along thecochlear nerve in cochlea when the carrier is inserted in cochlea.

A computer readable medium. In an aspect, the method steps may be storedon or encoded as one or more instructions or code on a tangiblecomputer-readable medium. The computer readable medium includes computerstorage media adapted to store a computer program comprising programcodes, which when run on a processing system causes the data processingsystem to perform at least some (such as a majority or all) of the stepsof the method described above, and in the claims.

By way of example, and not limitation, such computer-readable media cancomprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage,magnetic disk storage or other magnetic storage devices, or any othermedium that can be used to carry or store desired program code in theform of instructions or data structures and that can be accessed by acomputer. Disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media. Inaddition to being stored on a tangible medium, the computer program canalso be transmitted via a transmission medium such as a wired orwireless link or a network, e.g. the Internet, and loaded into a dataprocessing system for being executed at a location different from thatof the tangible medium.

In an aspect, a data processing system comprising a processor adapted toexecute the computer program for causing the processor to perform atleast some, such as a majority or all, of the steps of the methoddescribed above and in the claims.

It is intended that the structural features of the devices describedabove, either in the detailed description and/or in the claims, may becombined with steps of the method, when appropriately substituted by acorresponding process.

As used, the singular forms “a,” “an,” and “the” are intended to includethe plural forms as well (i.e. to have the meaning “at least one”),unless expressly stated otherwise. It will be further understood thatthe terms “includes,” “comprises,” “including,” and/or “comprising,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. It will also be understood that when an element is referred toas being “connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element but an intervening elementsmay also be present, unless expressly stated otherwise. Furthermore,“connected” or “coupled” as used herein may include wirelessly connectedor coupled. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items. The steps ofany disclosed method is not limited to the exact order stated herein,unless expressly stated otherwise.

It should be appreciated that reference throughout this specification to“one embodiment” or “an embodiment” or “an aspect” or features includedas “may” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment of the disclosure. Furthermore, the particular features,structures or characteristics may be combined as suitable in one or moreembodiments of the disclosure. The previous description is provided toenable any person skilled in the art to practice the various aspectsdescribed herein. Various modifications to these aspects will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other aspects.

The claims are not intended to be limited to the aspects shown herein,but is to be accorded the full scope consistent with the language of theclaims, wherein reference to an element in the singular is not intendedto mean “one and only one” unless specifically so stated, but rather“one or more.” Unless specifically stated otherwise, the term “some”refers to one or more. Accordingly, the scope should be judged in termsof the claims that follow.

The invention claimed is:
 1. A signal processing method for reducingelectromagnetic noise induced in a component of a hearing aid, whereinthe hearing aid comprises a battery, an active component powered by thebattery, a noise sensitive component providing an output signal, and aprocessor powered by the battery, when the active component is operatedso as to cause a power drain from the battery the processor isconfigured to obtain a measure of the power drain from the battery, themethod comprising: monitoring power drain or usage from the battery viathe processor, and basing or adapting a noise reduction processing,which is performed on the output signal from the noise sensitivecomponent to reduce electromagnetic noise induced by the activecomponent, on the monitored current power usage of the battery, whereinthe processor determines, based on the current power usage, if theactive component is in an active state or a non-active state, and themethod further comprises, provided the active component is determined tobe in an active state, applying noise reduction algorithm to reducenoise induced by the active component on the output signal.
 2. Themethod according to claim 1, wherein the noise induced in the noisesensitive component is in the audible frequency range.
 3. The methodaccording to claim 1, wherein the noise sensitive component is at leastone of: a telecoil, a receiver or a microphone.
 4. The method accordingto claim 1, wherein an estimate of the induced noise is predeterminedand stored before being used for reducing or removing the induced noise.5. A signal processing method for reducing electromagnetic noise inducedin a component of a hearing aid, wherein the hearing aid comprises abattery, an active component powered by the battery, a noise sensitivecomponent providing an output signal, and a processor powered by thebattery, when the active component is operated so as to cause a powerdrain from the battery the processor is configured to obtain a measureof the power drain from the battery, the method comprising: monitoringpower drain or usage from the battery via the processor, and basing oradapting a noise reduction processing, which is performed on the outputsignal from the noise sensitive component to reduce electromagneticnoise induced by the active component, on the monitored current powerusage of the battery, wherein the noise contribution from supply currentis estimated by averaging over different instances of the noise.
 6. Asignal processing method for reducing noise induced in a component of ahearing aid, wherein the hearing aid comprises a battery, an activecomponent powered by the battery, a noise sensitive component providingan output signal, and a processor powered by the battery, when theactive component is operated so as to cause a power drain from thebattery the processor is configured to obtain a measure of the powerdrain from the battery, the method comprising: monitoring power drain orusage from the battery via the processor, and basing or adapting a noisereduction processing of the output signal from the noise sensitivecomponent on the monitored current power usage of the battery, whereinan average waveform is trained in advance or during startup of thehearing instrument, or while the hearing instrument is in a program,where the active component is not used.
 7. A signal processing methodfor reducing electromagnetic noise induced in a component of a hearingaid, wherein the hearing aid comprises a battery, an active componentpowered by the battery, a noise sensitive component providing an outputsignal, and a processor powered by the battery, when the activecomponent is operated so as to cause a power drain from the battery theprocessor is configured to obtain a measure of the power drain from thebattery, the method comprising: monitoring power drain or usage from thebattery via the processor, basing or adapting a noise reductionprocessing, which is performed on the output signal from the noisesensitive component to reduce electromagnetic noise induced by theactive component, on the monitored current power usage of the battery,and measuring the supply current and establishing an estimate of thecurrent influencing the magnetic field in the noise sensitive component.8. A signal processing method for reducing electromagnetic noise inducedin a component of a hearing aid, wherein the hearing aid comprises abattery, an active component powered by the battery, a noise sensitivecomponent providing an output signal, and a processor powered by thebattery, when the active component is operated so as to cause a powerdrain from the battery the processor is configured to obtain a measureof the power drain from the battery, the method comprising: monitoringpower drain or usage from the battery via the processor, and basing oradapting a noise reduction processing, which is performed on the outputsignal from the noise sensitive component to reduce electromagneticnoise induced by the active component, on the monitored current powerusage of the battery, wherein supply current or changes in supplycurrent are estimated based on a measurement of a resistor ortransformer or by any other current measurement techniques, such as byuse of a Hall sensor.
 9. A hearing aid comprising a battery, an activecomponent powered by the battery, a noise sensitive component and aprocessor powered by the battery, the processor configured to obtain ameasure of power drain from the battery, wherein the active component isconfigured to be operated so as to cause a power drain from the battery,the processor is configured to apply a noise reduction algorithm, whichreduces electromagnetic noise induced by the active component into anaudio input signal from the noise sensitive component, based on thepower usage of the battery, wherein the processor is further configuredto determine, based on the current power usage, if the component is inan active state or a non-active state, and to apply noise reductionbased on the activity state of the component.
 10. The hearing aidaccording to claim 9, wherein the active component includes a radiofrequency transceiver.
 11. The hearing aid according to claim 9, whereinthe noise sensitive component is at least one of a coil, a telecoil, ora microphone.
 12. A binaural hearing aid system comprising two hearingaids each according to claim
 9. 13. A binaural hearing aid systemcomprising two hearing aids each according to claim
 10. 14. A binauralhearing aid system comprising two hearing aids each according to claim11.
 15. The method according to claim 5, wherein the noise sensitivecomponent is at least one of: a telecoil, a receiver or a microphone.16. The method according to claim 6, wherein the noise sensitivecomponent is at least one of: a telecoil, a receiver or a microphone.17. The method according to claim 7, wherein the noise sensitivecomponent is at least one of: a telecoil, a receiver or a microphone.18. The method according to claim 8, wherein the noise sensitivecomponent is at least one of: a telecoil, a receiver or a microphone.